The invention relates to an exhaust-air purifying unit comprising at least one fan for moving exhaust air, a heat exchanger in which the exhaust air is cooled, and a mechanical filter. Purifying units of this type are particularly useful in connection with yarn finishing units.
German Offenlegungsschrift 3,734,388 discloses an exhaust-air purifying unit which directs an exhaust-air flow through two successive heat-exchanger stages and finally through a mechanical filter. A fan is provided for drawing off the exhaust-air flow. In the known arrangement, the aim is to precipitate the condensible harmful substances in the exhaust-air flow by a considerable cooling in the two heat-exchanger stages so that only a small quantity of harmful substances is fed to the mechanical filter. Or account of the two heat-exchanger stages and the pipelines connecting them, the known arrangement requires a considerable construction space, which is not available in all installations of the textile-processing or plastics-processing industry and is not available at all if retrofitting with an existing exhaust-air purifying unit is to be carried out.
Furthermore, units for adsorption and dust separation by so-called washers are known in which the exhaust-air flow is passed through a plurality of washing stages which in each case comprise a pebble bed, a washing-liquid feed, a drop separator and a washing -liquid return. Washers of this type likewise require a considerable construction space, since the intermixing of the washing liquid with the exhaust air is achieved only when the pebbles have a large contact surface area, there also being the problem that the pebble bed becomes clogged with harmful substances.